Abstract: Aiming at the problem of density effect in the process of cyclone classification of iron ore,according to the lowgrade characteristics of iron ore resources in China,quartz-magnetite (1 ∶1) artificial mixed ore were taken as the research object,and hydrocyclone with diameter 100 mm was used to carry out physical experiments. The influences of changes of the underflow orifice diameter on the particle density effect in the classification process were systematically investigated. The results showed that the recovery to underflow of high-density magnetite component is larger,and the difference of recovery to underflow between high-density magnetite component and quartz component is the most obvious near the middle particle size (45 μm). With the increase of underflow orifice diameter,the difference of recovery to underflow decreases to about 10%. Increasing the diameter of underflow orifice can reduce the difference in cut size and classification sharpness caused by the density effect,and weaken the interaction of different density components due to the density effect. The fine particles (d≤ 20 μm) misplaced into underflow products are mainly composed of high-density fine-grained magnetite component,while the coarse (d>20 μm) particles misplaced into overflow products are mainly composed of low-density coarse-grained quartz component. The research results could provide a theoretical basis for weakening the influence of particle density effect in the classification process.

Key words: hydrocyclone,classification,underflow orifice diameter,multi-component iron ore,density effect